Irises as a group aren’t among my favorite plants. The individual flowers are exquisite, of course, but the flowering period isn’t all that long, and many of them just aren’t all that interesting when they aren’t in bloom. There are exceptions, though. One that I’ve found to earn its keep through much of the growing season is ‘Gerald Darby’.
This selection is most often listed under Iris x robusta – a hybrid of two native American species: I. versicolor and I. virginica – though you’ll sometimes see it sold as a cultivar of one of those parent species, or as a Siberian-Louisiana Hybrid. It’s been around since the late ’60s but still isn’t widely available, and I can’t imagine why, considering how many good qualities it has to offer.
‘Gerald Darby’ in Spring
The best ornamental feature of this selection is its spring foliage, which ranges from dusky purple to purple-black (usually, the cooler the weather, the darker the foliage).
Above is ‘Gerald Darby’ with ‘Angelina’ sedum (Sedum rupestre) [April 19, 2009]. Below is a much quieter combination of ‘Gerald Darby’ with purple-leaved Japanese parsley or Japanese honewort (Cryptotaenia japonica f. atropurpurea) [April 11, 2010].
The growing tips are bright green, but the purple lingers at the base of the plants for a few more weeks. Below is a shot from May 1, 2008. At this point, the plants were 12 to 18 inches tall. You can see that some of the leaves are already starting to arch.
By late May, the leafy clumps are about 3 feet tall. The purple at the leaf bases is hardly noticeable at this point, but there’s a new source of interest: slender but sturdy, near-black flowering stems that spike up through the foliage.
The images above and below are from May 22, 2010. The one below – a later view of the April 11 shot with purple-leaved Japanese parsley – also includes some shoots of blue-leaved rose (Rosa glauca).
‘Gerald Darby’ in Summer
Early summer is prime time for the bloom display of ‘Gerald Darby’ here in southeastern Pennsylvania. Each stalk usually carries several buds, so there’s a good show of nicely distributed flowers. Below is a June 1 shot of the combo also featured above.
The flowers are rather delicate-looking, and the purple-blue color isn’t especially vibrant. For a few years, my original clump flowered against a clump of ‘Amazone’ tuberous Jerusalem sage (Phlomis tuberosa) [below: June 1, 2006].
The pairing was pretty but wispy and not “wow.” Fortunately, the vigorous plants bulk up quickly, so within a few years, I had enough divisions to be able to experiment with different settings.
Adding some dark foliage gave the flowers a much more interesting background. The image below, from June 28, 2010, includes a red Japanese maple (Acer palmatum).
Above is ‘Gerald Darby’ against Diabolo ninebark (Physocarpus opulifolius ‘Monlo’), which did a great job of echoing the dark staining in the iris stems [May 26, 2010]. Below, the background is ‘Velvet Cloak’ smokebush (Cotinus coggygria) [May 23, 2010].
Chartreuse foliage did an even better job creating the wow factor I was hoping for.
Below is a shot from June 13, 2009, with ‘Angelina’ sedum and golden catalpa (Catalpa bignonioides ‘Aurea’).
‘Gerald Darby’ in Fall
After flowering, this iris rarely sets seed, so it’s just a foliage accent – a job it does quite well as long is the weather isn’t too dry. My soil tends to be on the moist side but has some dry periods each summer and it normally continues to look good for months. The image below is from August 23, 2006.
For comparison, here’s a view of that same area of the garden: from June 26, 2006 on the left and September 19, 2006 on the right.
By mid-fall – or earlier if the weather is very dry – the clumps collapse messily [below, October 22, 2006]. Still, that seems a fair exchange for the extended show of new shoots, flowers, and foliage.
Before the collapse, ‘Gerald Darby’ usually reaches about 4 feet tall for me, but I’ve seen the leafy clumps reach 5 feet or more in very rich, moist soil. It’s reportedly hardy in Zones 4 to 9.
Current web sources for ‘Gerald Darby’ include ForestFarm, Secret Garden Growers, and McClure & Zimmerman. If you have trouble finding it, you might consider trying a cultivar called ‘Dark Aura’ instead; I’ve not seen it in person, but the descriptions make it sound just like ‘Gerald Darby’. ‘Dark Aura’ is currently listed by Plant Delights Nursery and Iris City Gardens.